1. Field of the Invention
The present invention relates to a process for the production of a laminated product from a polyvinylidene fluoride.
2. Description of the Background
Polyinylidene fluoride has been attracting considerable attention as highly functional plastics with superior resistance to chemicals, resistance to heat, weather resistance, and capability of preventing staining. Utilizing these superior characteristics, experiments have been conducted in applying these resins as anticorrosion lining materials for use with various types of chemicals. However, because polyvinylidene fluoride has poor flexibility and is chemically stable, adhesion between polyvinylidene fluoride and the metals used to fabricate tanks is poor so they are considered to be unsuitable for tank linings.
Accordingly, there is a strong demand for a method for laminating these resins with nitrile rubber or the like which has superior capabilities for bonding to metals. A process for laminating polyvinylidene fluoride with rubber must be designed so as to improve inherently poor adherence capability of the polymer to rubber. One of the well known methods employs adhesion by vulcanization at a high temperature, equivalent to the melting point of the polyvinylidene fluoride or higher. In another method which is also well known, the surface of the polyvinylidene fluoride is first subjected to an activation treatment such as a corona discharge treatment or a sodium treatment and then adhered to the rubber via an adhesive under vulcanization.
The high temperature vulcanization method, however, produces a poor outside appearance, with bubbles and undulations appearing on the surface of the polyvinylidene fluoride, while a suitable adhesive which is resistant to heat and to steam has not yet been found for the latter method which uses an activated adhesive. For these reasons, a laminated product which can be practically used has not yet been produced.
In view of this situation, the inventors of the present invention have undertaken extensive studies in order to develop a method for manufacturing a laminated product which imparts superior adhesive strength between polyvinylidene fluoride and rubber and which is suitable for industrial applications. As a result, the inventors have found that such a laminated product can be obtained by a process using an adhesive which comprises a rubber-like polymer and specific types of material. Such a finding has led to the completion of the present invention.